1. Field of the Invention
The invention is in the field of stiff structural members, such as aircraft spars and other structural members that undergo cantilever forces or cantilever-like forces.
2. Description of the Related Art
Mechanically stiff structural members, such as wing spars, typically have very low damping constants. Traditionally, stiff structural members such as those used in aircraft spars have been subject to resonances that limit the performance capabilities of the structure. This results in structures having distinct resonances which can be excited, such as (for wing spars) by flight conditions. These resonances can be in the form of the fundamental cantilever resonance frequency, or can be in the form of higher modes such as those encountered during “flutter” of aerodynamic control surfaces, in which the resonant characteristics of the wing couple to the airflow past the wing. Resonances can cause reduced range/performance, difficulty in attitude control, and flutter and/or structural failure, to name just a few potential problems. FIG. 1 illustrates resonance in a typical spar 10.